Leak-resistant dry cell



Aug. 29, 196 7 Y 3,338,750

LEAK-RESISTANT DRY CELL Original Filed May 1, 1961 2 Sheets-Sheet 1INVENTOR. LEWIS F. URRY A T TORNFV Aug. 29, 1967 URRY 3,338,750

LEAK-RESISTANT DRY CELL Original Fild May 1, 1961 2 Sh 2 86 :.I: I. 2.x:

I02 C 90 1: mg .1) INVENTOR. 104 g: m LEWIS F. URRY ATTORNEY UnitedStates Patent ,3 Y LEAK-RESISTANT DRY CELL Lewis F. Urry, Cleveland,Ohio, assignor to Union Carbide Corporation, a corporation of New YorkOriginal application May 1, 1961, Ser. No. 106,760. Divided and thisapplication Aug. 27, 1965, Ser. No. 483,053

7 Claims. (Cl. 136-107) This application is a division of applicationSer. No. 106,760, filed on May 1, 1961, now abandoned;

This invention relates to leak-resistant dry cells of the type having aclosed container surrounding the cell proper.

The so-called Leclanch dry cell used for flashlights, portable radios,photofiash and other devices has gone through an evolution ofimprovements during the past decade or more in an attempt bymanufacturers to prevent leakage from the cell during and after its use.Despite the many proposals, however, that have been advanced, therestill remains a need for a better leak-resistant dry cell.

One proposal that has been adopted commercially is to encase aconventional dry cell within a closed container. This dry cellconstruction, however, has been plagued by certain difiiculties. Forexample, one type of container which has ,been used comprises a metalcontainer, but this suffers from the disadvantage that the metal issubject to corrosion by liquid exudate from the cell. To avoid thisdisadvantage, non-corrodible containers have also been utilized. Theprincipal difliculty, however, with non-corrodible containers is thatthey do not possess the mechanical strength of metal containers andsufler from the disadvantage that they may often be damaged, and evendestroyed, by the pressure which builds up from the formation of gaswithin the cell. Several suggestions have been advanced for overcomingthis disadvantage of non-corrodible containers in which the attempt hasbeen made to continuously vent the gas from the cell. Thus, in priorconstructions, the gas has been vented, for example, through the carbonelectrode, and then out through venting means provided in the topclosure of the container. The difiiculty, however, with thesesuggestions is that the venting paths, for instance through the carbonelectrode, have been prone to obstruction by cell exudate, therebyblocking the passage of gas from the cell.

In addition to obstructing the venting paths provided in the cell, thiscell exudate has also given rise to other serious problems. For example,one diflicult problem has been the tendency for metal formed in solutionby normal consumption of the metal electrode to deposit out from thecell exudate in the form of spongy tree-like deposits. These metaldeposits have formed principally on top of the depolarizer mix betweenthe electrodes of the cell and have been particularly troublesome fromthe standpoint of cell performance, for they very likely can short outthe cell by establishing short-circuit paths between the cellelectrodes. Thus, the cell in many instances may be drained of its powereven though it is not in use.

It is therefore an important object of the invention to provide animproved gas venting path in a leak-resistant dry cell particularly ofthe type of construction utilizing a non-corrodible container, which gasventing path is not prone to obstruction during use of the cell.

More specifically, it is another object to provide such a ga ventingpath in a leak-resistant dry cell while at the same time preventing theestablishment of short-circuit paths between the electrodes of the cell.

Briefly, these and other objects are achieved by the invention whichcomprises a partition seal between the closure and depolarizer mix of aleak-resistant dry cell defining a barrier which protects at least oneof the electrodes of the cell from contact by liquid cell exudate andalso providing a path for venting gas from the cell.

I In the accompanying drawings:

FIG. 1 is a vertical elevation partially in section of a leak-resistantdry cell embodying the invention;

FIG. 2 is a similar view of the top portion only of a dry cell showinganother embodiment of the invention;

FIG. 3 is similar to FIG. 2 showing another embodiment of the invention;

FIG. 4 is a similar view of another dry cell construction showinganother embodiment;

FIG. 5 is similar to FIG. 4 showing another embodiment;

FIG. 6 is similar to FIG. 2 showing another embodiment;

FIG. 7 is similar showing still another embodiment;

FIG. 8 is similar showing yet another embodiment;

FIG. 9 is similar showing a further embodiment; and

FIG. 10 is a vertical elevation of still another dry cell constructionembodying the invention.

Referring to the drawings, a leak-resistant dry cell of a constructionotherwise conventional but embodying the invention is shown in FIG. 1.The cell comprises a cup electrode 10 of a consumable metal, forinstance, zinc having therein a central electrode 12 'of porous carbonembedded within a depolarizer mix 14 and an immobilized electrolyte 16suitably in the form of a conventional paste. At the top of the celljust above the depolarizer mix 14 and so placed as to define a lowerfree space 18 around the carbon electrode 12 and an upper free space 20is a partition seal comprising a truncated cone 22 fitted tightly aroundbut not necessarily sealed to the carbon electrode 12 and firmlyembedded in the depolarizer mix 14 at the junction 24. A hard rigidsealing layer 26 is applied over both the depolarizer mix 14 andelectrolyte paste 16 and secures the truncated cone 22 rigidly in placeby overlying at least its outermost edges. The truncated cone 22 iscomposed suitably of paper or other fibrous material protected againstpenetration of liquid by a coating of a liquid repellent material, forexample, polyethylene. The sealing layer 26 preferably is composed of ahard variety of asphalt or wax, for example.

A preferred top closure for the cell comprises a flanged metal cap 28fitted on top of the carbon electrode 12 and an insulating washer 30carried by the cap 28 on which rests the inner peripheral edges of ametal washer 32 whose outer edges are locked in liquid-tight engagementwith a jacket 34. The jacket 34 preferably is noncorrodible, it beingcomposed, for example, of paper, and fits the cup electrode 10 ratherloosely, thereby providing a supplementary chamber 36 for receivingliquid exudate from the cell. The jacket 34 also has locked to it ametallic false bottom 38 which underlies and is in contact with thebottom of the cup electrode 10.

During use of the cell, especially under severe conditions, gas isreleased. The .gas follows a path through or around the carbon electrode12 in the depolarizer mix 14, into the free space 18 and then throughthe electrode 12, into the upper free space 20 where eventually the gasescapes from the cell, for instance, by being vented from between thedisplaceable edges of metal washer 32 and insulating washer 30 of thetop closure. Alternatively, the gas may also be passed through thecarbon electrode 12 and into the upper free space 20 or from within thefree space 18 between the electrode 12 and the truncated cone 22, andthen out of the cell through the top closure,

the latter being the gas venting path, for instance, when a carbonelect-rode impregnated against penetration of both liquid and gas isused. At the same time, liquid is exuded through the depolarizer mix 14towards the cup electrode 10, but is barred from entering the upper freespace 20 by the hard rigid sealing layer 26, thereby preventing theliquid exudate from blocking the passage of gas through the top closure.The junction 24 aids in preventing displacement of the truncated cone 22by gas pressure generated within the cell, but more importantly, itprovides a barrier which effectively blocks off liquid from creepinginto the free space 1 8 from beneath the sealing layer 26. To establishthe juncture 24, the truncated cone 22 should be firmly and rigidlyembedded within the depolarizer mix 14. In a D-size dry cell, thetruncated cone 22 (or any of the partition seals to be hereinafterdescribed) should be embedded in the depolarizer mix 14 to a depth ofabout /a inch and in AA-size cell to a depth of about inch. Thus, itwill be seen by this construction that liquid exudate is not only barredfrom blocking the passage of gas through the free space 18 and carbonelectrode 12 or from escaping out of the cell by way of the free space18, but also is barred from contacting the carbon electrode 12 and fromestablishing short-circuit paths between it and the cup electrode 10 bythe deposition of spongy zinc metal over the depolarizer mix 14. Aninsoluble salt layer which normally forms on the surfaces of thedepolarizer mix 14 during discharge protects the cell from being shortedout by these metal deposits between the depolarizer mix 14 and the cupelectrode 10. It should be noted that the partition seal of thisinvention takes advantage of this salt layer which serves to provide aseal around the junction 22 which liquid cannot penetrate.

As shown in FIGS. 2 to 10 inclusive, the principles of the invention maybe achieved in a number of ways and are applicable to a variety of drycells. For example, referring to FIG. 2, the partition seal may comprisea tube 40 and a washer 42 so arranged as to define a lower free space 44and an upper free space 46. The tube 40 is provided about the carbonelectrode 12 and is embedded in the depolarizer mix 14 at the junction24. The washer 42 fits rather snugly around the carbon electrode 12 andrests on the top edges of the tube 40. A hard rigid sealing layer 48 ofasphalt or wax is applied over the depolarizer mix 14 and electrolytepaste 16 and secures the seal rigidly in place by overlying the outeredges of the washer 42. In FIG. 3 the washer 42 is sealed to the carbonelectrode 12 by the sealing layer 48 which surmounts it, the gas ventingpath in this instance being solely through the electrode 12. Both thetube 40 and washer 42 suitably are composed of paper or other fibrousmaterial rendered repellent to liquid by a coating of polyethylene, forexample.

The constructions thus far desmribed have been characterized by the factthat liquid is immobilized by a hard rigid sealing layer applied to thetop of the depolarizer mix and electrolyte paste of the cell. This makesit possible to utilize practically the whole of the space between thedepolarizer mix and the top closure for venting gas from the cell.However, it is entirely possible to construct a dry cell embodying theprinciples of the invention in which the sealing layer is eliminated.

Such a. construction is shown in FIG. 4. As shown, a dry cell isconstructed utilizing a partition seal similar to that just describedbut in which the washer 42 is of a larger diameter and rests on theupper edges of the cup electrode 1 defining an exudate chamber 50. Thewasher 42 is preferably sealed to both the tube 40 and cup electrode bya thin layer 52 of asphalt, for example, to prevent against exudateescaping out of the chamber 50. Alternatively, a thicker sealing layer54 suitably of Wax may be used for the same purpose as shown in FIG. 5.Also shown in FIG. 5, an insulating washer 56 suitably of polyethyleneoverlies the depolarizer mix 14 and prevents spongy zinc metal frompenetrating through the before mentioned salt layer, thereby preventingthe cell from otherwise being shorted out between depolarizer mix 14 andcup electrode 10. The dry cell constructions shown in FIGS. 4 and 5differ from that illustrated in FIG. 1, for example, in that a topclosure comprising a one-piece metal cover 58 having an opening 60 forventing gas is utilized.

Another construction which may be used is shown in FIG. 6. Here, a drycell incorporates a partition seal of one piece composed of a tube 62embedded in the depolarizer mix 14 at the junction 24 as in theconstructions described, but which differs in that the tube 62 extendsup to the metal washer 32 of the top closure and defines an inner freespace 64 and an outer exudate chamber 66. The tube 62 preferably iscomposed of a plastic material, polyethylene, for example, and is bondedto the metal washer 32 by a thin layer 68 of cement, a vinyl resinhaving been used successfully for this purpose. It will be observed inthis construction that gas may be vented through the inner free space 64and directly out the top closure of the cell. FIG. 7 shows amodification of this construction in which the tube 62 is provided witha flanged end 70 which fits over the flanged cap 28 of the top closureand replaces the insulating washer of the closure. A coating 72 suitablyof vinyl resin, for example, may also be applied to the underneath sideof the metal washer 32 to prevent against its being corroded. Also shownin FIG. 7, a thin layer 74 of grease, for example, to prevent ingress ofoxygen may be provided over the depolarizer mix 14. This grease layer aswell as the before mentioned insulating washer may be used in any of theconstructions described.

Still another construction which may be used is shown in FIG. 8. A drycell as shown is constructed with a partition seal which comprises amolded plastic washer 76 fitted rather tightly within the upper edges ofthe cup electrode 10 overlying the electrolyte paste 16 and having anintegral depending flange 78 embedded within the depolarizer mix 14 atthe junction 24. Preferably, the upper edges of the cup electrode 10 arecurled over on top of the washer 76 to rigidly secure it in place withinthe cell. It will be noted in this construction that liquid exudate isimmobilized as in the construction shown in FIGS. 2 and 3, and that theWhole of the free space above the depolarizer mix 14 is utilized forventing gas from the cell.

The constructions described in which the partition seal embodying theinvention is of one piece are advantageous because placement of the sealis greatly facilitated during manufacture of dry cells. It will beunderstood that any of the constructions described, for example that ofFIG. 4 may be embodied in one piece such as shown in FIG. 9. A dry cellthus is constructed utilizing a partition seal of a molded plastic disc80 which is supported within the cup electrode 10 at its upper edges.The disc 80 has an aperture at its center for tightly receiving thecarbon electrode 12, and also has an integral tubular flange 82depending therefrom the lower edges of which are embedded within thedepolarizer mix 14 at the junction 24. Preferably, a thin layer 84 of asealant, for example, vinyl resin, seals the disc 80 to the metal washer32 of the top closure.

A different version of a dry cell incorporating the invention is shownin FIG. 10. The dry cell which is shown is substantially disclosed andclaimed in US. Patent No. 2,605,299 issued to J. P. Teas on July 29,1952, and comprises a non-corrodible jacket 86 suitably of paper havinga metallic one-piece top closure 88 locked to its upper edges and a cupelectrode 90 of carbon molded in juxtaposition to and in adherentcontact with the inner surfaces of the jacket 86 and top closure 88, thecup electrode 90 being suitably molded in place by injection moldingtechniques. A central electrode 92 of a consumable metal, for example,zinc having a generally X shaped cross section and provided with aconventional separator 94 of a bibulous paper is embedded within adepolarizer mix 96 Which substantially fills the cup electrode 90 butwhich leaves a space through which the stem of the central electrode 92extends at the bottom open end of the cup electrode 90. A metallicbottom closure 98 is locked to the bottom edges of the jacket 86 withwhich makes contact the stem of the central electrode 92. Between thebottom closure 98 and depolarizer mix 96 and defining an inner freespace 100 and an outer free space 102 is a partition seal comprising atubular sleeve 104 of a diameter slightly less than that of the cupelectrode 90, one end of which is embedded Within the depolarizer mix 96at the junction 106 and the other end of which is locked in theengagement between the bottom closure 98 and jacket 86. A hard rigidsealing layer 108 suitably of wax is applied over the depolarizer mix 96and overlies both the bottom closure 98 and tubular sleeve 104, andprevents liquid from entering the free space 100 within the bottom ofthe cell. With this construction, it will be seen that the dry cellfunctions essentially the same as previously described except that gasis vented through the outer free space 102 and then out of the cell frombetween the locked junction of the bottom closure 98 and jacket 86.

A number of dry cells embodying the invention have been made and testedover a wide range of conditions. These tests demonstrated theeflectiveness of the invention, for cells otherwise identical inconstruction but lacking the structural features of the invention showedevidence of leakage from and/ or bulging of the cell container whilethose cells embodying the invention showed little or no evidence of gaspressure build-up and consistently demonstrated superior leakproofness.The eilectiveness of the invention was further demonstrated by the factthat the dry cells of the invention had a longer life and did not shortout during the tests.

It will be understood that many changes and modifications of the drycell constructions described herein may be made without departing fromthe spirit and scope of the invention.

What is claimed is:

1. In a leak-resistant dry cell comprising a cup elec- I trodecontaining depolarizer mix, electrolyte and a second electrode embeddedwithin said depolarizer mix, the combination of a closure for said cell,said closure being spaced from said depolarizer mix and having gasventing means therein, a partition seal positioned between saiddepolarizer mix and said closure within the space provided therebetweenand defining a barrier which protects at least one of said electrodesagainst contact by liquid exudate from said cell, said seal beingembedded within said depolarizer mix and forming a juncture whichprohibits the passage of said liquid exudate beneath said seal, and ahard rigid sealing layer disposed within the space provided between saidclosure and said depolarizer mix, said hard rigid sealing layer beingpositioned over said depolarizer mix and electrolyte and overlying atleast a portion of said partition seal, said seal in conjunction withsaid gas venting means in said closure providing a liquid-free path forventing gas from said cell.

2. A leak-resistant dry cell as defined by claim 1 in which said cupelectrode is composed of a consumable metal and in which said secondelectrode is composed of car n,

3. A leak-resistant dry cell as defined by claim 1 in which said cupelectrode is composed of carbon and in which said second electrode iscomposed of a consumable metal.

4. A leak-resistant dry cell as defined by claim 2 in which saidpartition seal comprises a truncated cone fitted around said carbonelectrode and at its lower edges embedded within said depolarizer mixand in which said sealing layer overlies the embedded edges of saidtruncated cone.

5. A leak-resistant dry cell as defined by claim 2 in which saidpartition seal comprises a tube provided about said carbon electrode andat its lower edges embedded within said depolarizer mix, and a washerfitted around said carbon electrode and resting on the upper edges ofsaid tube and in which said sealing layer overlies the peripheral edgesof said washer.

6. In a leak-resistant dry cell comprising a jacket, a metal top closurelocked in engagement with said jacket and a cup electrode of carbon injuxtaposition to and in adherent contact with said jacket and said topclosure containing depolarizer mix and a central electrode of aconsumable metal embedded within said depolarizer mix, the combinationof a bottom closure locked in engagement with said jacket, said bottomclosure having gas venting means therein; and a partition sealpositioned between said depolarizer mix and said bottom closureproviding a free space between said seal and said cup electrode anddefining a barrier which protects said cup electrode from contact byliquid exudate from said cell, said seal being embedded within saiddepolarizer mix and forming a juncture which prohibits the passage ofsaid liquid exudate beneath said seal and into said free space, saidseal in conjunction with said gas venting means in said bottom closureproviding a path for venting gas from said cell. I

7. A leak-resistant dry cell as defined by claim 6 in which saidpartition seal comprises a tubular sleeve embedded within saiddepolarizer mix and at its lower end locked in engagement between saidbottom closure and said jacket.

References Cited UNITED STATES PATENTS 2,850,558 9/1958 Urry 136-4333,016,414 1/1962 Priebe 136-107 3,051,769 8/1962 Jammet 13 6l333,179,537 4/1965 Reilly 136-107 X 3,214,298 1 0/ 1965 Urry 136107FOREIGN PATENTS 1,213,467 11/1959 France.

792,152 3/1958 Great Britain.

WINSTON A. DOUGLAS, Primary Examiner. B, J. OHLENDORF, A. SKAPARS,Assistant Examiners.

1. IN A LEAK-RESISTANT DRY CELL COMPRISING A CUP ELECTRODE CONTAININGDEPOLARIZER MIX, ELECTROLYTE AND A SECOND ELECTRODE EMBEDDED WITHIN SAIDDEPOLARIZER MIX, THE COMBINATION OF A CLOSURE FOR SAID CELL, SAIDCLOSURE BEING SPACED FROM SAID DEPOLARIZER MIX AND HAVING GAS VENTINGMEANS THEREIN, A PARTITION SEAL POSITIONED BETWEEN SAID DEPOLARIZER MIXAND SAID CLOSURE WITHIN THE SPACE PROVIDED THEREBETWEEN AND DEFINING ABARRIER WHICH PROTECTS AT LEAST ONE OF SAID ELECTRODES AGAINST CONTACTBY LIQUID EXUDATE FROM SAID CELL, SAID SEAL BEING EMBEDDED WITHIN SAIDDEPOLARIZER MIX AND FORMING A JUNCTURE WHICH PROHIBITS THE PASSAGE OFSAID LIQUID EXUDATE BENEATH SAID SEAL, AND A HARD RIGID SEALING LAYERDISPOSED WITHIN THE SPACE PROVIDED BETWEEN SAID CLOSURE AND SAIDDEPOLARIZER MIX, SAID HARD RIGID SEALING LAYER BEING POSITIONED OVERSAID DEPOLARIZER MIX AND ELECTROLYTE AND OVERLYING AT LEAST A PORTION OFSAID PARTITION SEAL, SAID SEAL IN CONJUNCTION WITH SAID GAS VENTINGMEANS IN SAID CLOSURE PROVIDING A LIQUID-FREE PATH FOR VENTING GAS FROMSAID CELL.